Many techniques are currently available for determining an exposure for a photographic negative to be printed. These techniques, two of which are shown in FIGS. 1 and 2 described below, typically involve the measuring of selected densitometric characteristics of the individual negative.
Referring now to the series of FIGS. 1A, 1B, 1C, an exemplary photographic negative 10 is shown including a subject 12. In FIG. 1A, a region 14, shown in dashed-line, is identified as the region of negative 10 which is to be enlarged and printed. Many methods are available for identifying region 14, including that of simple visual examination and marking. Many other techniques, both simple and complex, will be readily known to those possessing ordinary skill in the art.
FIG. 1B illustrates in dashed line a region 16 enccompassing substantially the entirety of negative 10. In accordance with one prior art method, the entirety of region 16 is considered in measuring density characteristics of negative 10 to derive an exposure therefor. These density characteristics may include, for example, the large area transmissive density (LATD) of region 16, or the scanned transmissive density of a plurality of picture elements (pixels), i.e. small, discrete areas, distributed throughout the region.
As will be apparent from a consideration of FIGS. 1B and 1C, the latter showing the region 14 to be printed, the above-described method does not yield density characteristics which permit an optimal exposure calculation for that region. The above described method suffers from the inherent disadvantage that, while only a selected region 14 of negative 10 is printed, the exposure calculations for that region are based on densitometric measurements taken across the entirety of negative 10.
FIGS. 2A, 2B, and 2C, in which like elements to those of FIG. 1 are indicated by like reference numerals, are a like series of figures illustrating another known method of making densitometric measurements to calculate printing exposures. In the method shown in FIG. 2, densitometric characteristics of negative 10 are measured only over a selected, limited, region 18 (FIG. 2B) thereof. Region 18 is fixed in size relative to the size of negative 10, and is positioned by an operator (not shown) to overlay a region containing flesh tones and likely to comprise the main subject of the negative. Region 18 thus varies from negative to negative, being positioned by the operator to identify the main subject.
As will be apparent from a consideration of FIGS. 2A-2C, this last described method suffers from the inherent disadvantage of basing the exposure of the enlarged, cropped, printed region 14 of negative 10 on the small, flesh tone region 18. If the main subject does not include flesh tones, or if the background is not substantially neutral, the subsequently calculated exposure will not be optimal.
U.S. Pat. No. 3,708,676 to Huboi et al. (assigned to the assignee of the present invention) shows yet another method of measuring density characteristics for calculating the exposure of a photographic negative. In the Huboi et al. patent, discrete density measurements are taken at a plurality of pixels toward the centrl region of a negative, and a large, average density is taken about the periphery of the negative. Exposure of the negative is then calculated as a function of these density measurements. The method shown in Huboi et al., however, is not varied in accordance with different regions of the negative to be cropped, and thus will not provide optimal exposure control for cropped, printed negatives.